function TF = isfield(w,testField)
   %ISFIELD checks the presence of waveform fields.
   %   TF = ISFIELD(WAVEFORM,FIELD) returns an array the same size as
   %   WAVEFORM, containing logical 1 (true) where the elements of WAVEFORM
   %   contains the field specified by FIELD, and logical 0 (false) elsewhere.
   %   This is valuable since waveforms are capable of storing arbitrary
   %   user-defined fields. WAVEFORM can be of arbitrary size. FIELD may be a
   %   character string of a cell containing the same.
   %
   %   TF = ISFIELD(WAVEFORM,{FIELD1 FIELD2 FIELD3 ...}) checks for presence
   %   of several fields. In this use, WAVEFORM must be 1x1. TF is a matrix of
   %   logical 0 or 1 (true or false) with one element for each input FIELD.
   %   FIELD must be a cell array containing character strings.
   %
   %  See also ADDFIELD
   
   % AUTHOR: Michael West, Geophysical Institute, Univ. of Alaska Fairbanks
   % $Date$
   % $Revision$
   
   
   % READ & CHECK ARGUMENTS
   if (nargin~=2)
      error('Incorrect number of arguments');
   end
   if ~isa(w,'waveform')
      error('First input must be a waveform object');
   end
   if ~ischar(testField) && ~iscell(testField)
      error('Second argument must be a string or cell array of strings');
   end
   if ischar(testField)
      testField = {testField};
   end
   if numel(w)>1 && numel(testField)>1
      error('Multiple waveforms can only be tested against a single field at a time');
   end
   
   
   % GET LIST(S) OF STANDARD PLUS MISC. FIELDS
   if numel(w)==1
      waveformMiscFields = {get(w,'MISC_FIELDS')};
   else
      waveformMiscFields = get(w,'MISC_FIELDS');
   end
   waveformStandardFields = fields(waveform)';
   waveformFields = cell(size(w));
   for n = 1:numel(waveformFields)
      waveformFields{n} = [waveformStandardFields waveformMiscFields{n}];
   end
   
   
   % TEST AGAINST A SINGLE FIELD
   if numel(testField)==1
      TF = zeros(size(w));
      for n = 1:numel(TF)
         TF(n) = max(strcmpi(testField,waveformFields{n}));
      end
   end
   
   
   % TEST AGAINST MULTIPLE FIELDS
   if numel(testField)>1
      TF = zeros(size(testField));
      for n = 1:numel(TF)
         TF(n) = max(strcmpi(testField(n),waveformFields{1}));
      end
      
   end
end